There are many devices available for teaching basic skills to children or others in need of such instruction. These devices, often called instructional, i.e. teaching, toys teach skills such as letter (of the alphabet), word, number and color recognition.
One example of a teaching toy has cubes having datum, typically in the form of a letter, digit or color, disposed on one or more of its six sides. A student places a cube in a base receptacle, and a processor within the base identifies the datum. For example, if the cube had a letter "A" disposed on a side whose datum was to be identified, the processor would identify the datum as the letter "A". The toy may use a word processor and speaker to annunciate its identification.
Typically, in the case of teaching toys having a receptacle for receiving a cube, the side of the cube opposite the side with the datum thereon has a uniquely arranged array of exposed metal contacts. When the cube is inside the receptacle, electrical contact is made between the metal contacts and exposed receiving conductors in the receptacle. The processor in the base unit recognizes the unique arrangement as a code which identifies a specific datum.
A problem with exposed metal contacts and receiving conductors is that they become tarnished and dirty from exposure to the environment. After a period of time, the accumulation of dirt hinders or prohibits electrical conduction between the contacts and conductors. Thus, the toy malfunctions until the contacts are properly cleaned.
A second problem with exposed metal contacts and conductors is that a user may come in direct contact with voltage coupled to a contact. Direct contact with this voltage can cause a painful shock to the user.
As an alternative to exposed metal contacts, an array of mechanical switches may be disposed within the receptacle. The sides of the block have unique arrangements of protrusions which close (or open) a unique combination of the switches. The processor recognizes this unique combination as a code that it matches to the specific datum on any one side.
A problem with an array of switches is that the switches wear out with time. A problem with protrusions is that one or more may become damaged and cause the toy to malfunction. Replacement or repair of the damaged switches and protrusions is economically unfeasible and may be physically impossible as well.